Method of heating and furnace used therewith



Oct. 20, 1931. A. MEKLER METHOD OF HEATING AND FURNACE USED THEREWITH Filed March 11. 1927 5 Sheets-Sheet l METHOD OF HEATING AND'FURNACE USED THEREWITH Filed March 11, 1927 3 Sheets-Sheet 2 E 4 j m L. A. MEKLER METHOD OF HEATING AND FURNACE USED THEREWITH Oct 20, 1931.

5 Sheets-Sheet 3 Filed March l l, 1927 Patented Oct. 20, 1931 UNITED STATES PATENT OFFICE LEV A. MEKLER, OF CHICAGO, ILLINOIS, ASSIGNOR TO UNIVERSAL OIL PRODUCTS COM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF SOUTH DAKOTA IIYIIE'IIEIOI) OF HEATING AND FURNACE USED THERE'WITH Application filed March 11, 1927. Serial No. 174,683.

The present improvements relate more particularly to the idea of subjecting a ma-- is to control thetemperature of the gases generated, and a still further object is to recirculate regulated portions of the used gases of combustion to the heat generating zone, which recirculation is accomplished without the necessity of using extraneous and/or auxiliary equipment, such as fans, blowers, jets, and other similar instrumentalities now generally used for this purpose. As a feature of the invention this regulation of temperature is accomplished inside of the fur- 'nace and without the introduction of a substantial quantity of diluting air.

I The present invention is particularly applicable to the heating of hydrocarbon oil,

Where said oil passes through the heating zone in an elongated conduit of restricted cross section, although it is to be understood, as above set forth, that the invention in its broader aspects is not to be limited to this particular field.

In its general principle, the furnace heats by means of radiation from flues and by convection by the gases of combustion after the latter leave the radiating flues.- Radiation and convection 'act upon. the tubes simulta-' ,neously and in the same heating zone.

In the drawings, Fig. 1 is a vertical sectional view of a furnace built in accordance with the present invention.

Fig. 2 is a cross sectional view taken on line 22 of Fig. 1.

Fig. 3 is a cross sectional view taken on line 3-3 of Fig. 1.

Fig. 4 is a cross sectional View taken on line 4.'4= of Fig. 3.

Fig. 5 is a fragmentary sectional plan view of a slightly modified form of construction from that illustrated in Fig. 2.

Fig. 6 is a cross sectional view taken on line 6-6 of Fig. 5.

Fig. 7 is a cross sectional view taken on line 7-7 of Fig. 6.

Referring more in detail to the drawings, 1 designates the exterior top wall of a furnace having side walls 2. The furnace is provided with the usual arch 3 and an'insulating material 4 positioned both in the top wall and in the side and bottom walls, as shown. Adjacent the insulating material 4 in the side walls and on the interior of the furnace is a second wall of suitable refractory material 5. The walls 1 and 2 may be constructed of ordinary brick, the walls 5 may be of fire brick, and the insulation i may comprise any well known type of insulating material. The arch.3 may be curved as shown or, it may be fiat and may be constructed of any suitable type of refractory ma .a

The fuel, which may be either a powdered solid, gas or a liquid, is introduced to any one or more of the burners, illustrated diagrammatically at 6, said fuel first entering a heat generating and distibutin flue, desig nated diagrammatically at 7 an mounted in the floor of the furnace. By reference to Fig. 2 it is to be noted that provision is made for a number of oppositely disposed burners mounted on each side of the furnace and generating gases of combustion in spaced floor fiues 7. These flues 7 are formed by leaving spaces between the brick work comprising part of the floor of the furnace and designated diagrammatically at 8. By reference to Fig. 3 it will be particularly noted that this brick work designated 8 is mounted above the base or floor'9 of the furnace, being spaced therefrom and supported thereon by the supports illustrated diagrammatically at 10 for a purpose which will be more particularly hereinafter brought out.

as fire brick, and each flue 7 is provided with a cap or top 11 constructed of material which is preferably heat conductive, such as fire clay, aluminum oxide, magnesite, silicon carbide, special alloys, etc.

From the floor flues 7 the combustion gases are led into radiating side wall flues 12, located in either or both side walls of the furnace. The flues 12 are formed by leaving a longitudinal recess in the walls 5, which recess is closed by means of a slab 13, which may be made of the same material as the cover 11, possessing the properties of being highly heat conductive. It is obvious that by varying the thickness of the walls of the elements 11 and 13, or by careful selection of the material of which they are made. or both, it is possible to control very accurately the relative amount of radiation from the flues 7 and 12 as well as the ratio of total radiant heat to total convected heat. It is also obvious that thethickness of the walls of either of the elements 11 or 13 may vary intermediate their length.

\Vhile I have shown in the drawings a furnace equipped to illustrate under fired construction, that is with the heat generating and distributing flues mounted in the floor of the furnace, it is to be understood that the same principle can be applied with the heat generating and distributing flues mounted in the upper wall of the furnace, that is over fired construction, or the flues may be in the side walls, that is, side fired construction.

The numeral 14 designates tubes connected into a continuous coil through which the material to be heated may be passed, either countercurrent to the flow of combustion gases or the reverse. The combustion gases afterleaving the side wall radiating flues 12 discharge into the tube chamber 15. said gases directly contacting the tubes and thus heating by convection.

From the foregoing it is to be noted that in its general principle, the furnace heats the material being heated by means of radiation from wall flues, and simultaneously by convection by combustion gases after the latter leave the radiating flues. thus radiation and convection act upon the material being heated simultaneously and in the same heating zone.

As another feature of the present invention, means are provided for permitting controlled recirculation of spent combustion gases with attendant advantages. The flue arrangement, and the location of the burners is so designed as to give recirculation without the use of any external instrumentality, the burner acting as the injector. The control of the quantity of spent combustion gases which are recirculated is brought about by manipulation of the damper 21 in the flue 20, said flue having communication with the discharge flue 19 connected to the stack. The recirculation of some of the spent combustion gases by mixing them with the partially.or totally ignited spray from the burner facilitates combustion of the fuel, and dilutes the fresh gases of combustion, usually of very high temperature, with low temperature gases, thus reducing the temperature within the heat generating and distributing flues and prolonging the life of the material from which the latter are made; assists in regulating the ratio of radiated to convected heat, it being obvious that themore cooler gases recirculated, the lower will be the temperature in the flues and the less Will be the amount of heat radiated through the flues.

Since the spent combustion gases before leaving the furnace have to pass over and between the flues where they are heated, internal recirculation will result. This tends to equalize the furnace temperature between the top and bottom, and the degree of equalization can be further accurately controlled by controlling the relative amount of gases leaving the furnace through the flues 17 and 20, the former being controlled by means of the damper 16. The flue 17 has communicating branches 18, which latter in turn communicate with a discharge flue 19. Thus the temperature inside of the furnace is very accurately controlled without the introduction of substantial amounts of excess air.

By reason of the ledges or baflles 23 shown in Figure 1 of the drawings, the combustion gases issuing from flue 12 are directed into the coil 14 and prevented from passing downwardly along the radiant wall 13 between the same and the coil. In other words, the direct descent of the gases along the wall 13 is obstructed and the gases directed into the tube bank 14 to more efficiently heat the same by convection. This wall 13 is hotter than the space occupied by coil 14:, particularly the center of that coil through which the gases have to pass, and because of the heat radiated from flue 7, which will heat the descending gases of combustion, these gases will travel upwardly between wall 13 and tube bank 14 after they have come in contact with the tube bank. The advantages of this arrangement are that a much longer path is provided for the combustion gases within the furnace so that they remain longer in contact with the heat absorbing surfaces; the internal circulation increases the amount of gases in the furnace; and the internal circulation tends to equalize the combined action of convection and radiation on the tube surfaces, the gases passing upwardly between the wall 13 and the tube bank acting as a shield and diffuser of radiant heat from the wall 13.

As is illustrated at Fig. 3, the side wall flues 12 may be increased greatly in width intermediate the height of the flue.

The recirculation of spent combustion gases is further brought about by providing ducts 22 in the brick work 8 between the flues 7, which ducts communicate with the space 20 below the floor flues, and with flue 19.

Referring now more in detail to Figs. 5 to 7, both inclusive, the fundamental principle of construction is identical with the illustrations shown in Figs. 1 to 4:, both inclusive, except that each floor flue 7 instead of diverting the gases of combustion directly into the Wall flue, communicates through the passageway 7 with a second parallel fioor flue 7", which latter communicates with the sidewall flues 12, preferably on both sides thereof.

From the foregoing it will be apparent that I have devised a very efiicient furnace and method of heating whereby radiant and convected heat simultaneously act upon material being heated in the same heating zone, and as features of the invention, the ratio of convected to radiant heat can be definitely controlled; recirculation of regulated amounts of used combustion gases can take place without the employment of auxiliary means for effecting recirculation; the temperature within the heating zone can be accurately and uniformly cont-rolled, and-utmost efficiency obtained. Obvious mechanical changes and rearrangement of parts may take place It is to be understood that the novel idea of recirculation of used combustion gases includes recirculation before these used gases leave the heating chamber 15, or after they leave said heating chamber, or at a point before 0r afterthe completion of the combustion of the fuel.

I claim as my invention:

1. A furnace comprising, in combination, walls forming a heating chamber, one of said walls having a heat generating and distributing flue, means for feeding fuel to said heat generating and distributing flue, means for conducting'the products of combustion from 40 the latter into a similar flue in an adjacent wall, said flues having heat radiant portions so arranged as to radiate the heat from the products of combustion passing therethrough to the heating chamber, means to discharge the gases of combustion from the radiant flues into the heating chamber to heat same by convection.

2. A method of heating which comprises the steps of first causing generated gases of combustion to pass in a closed heat radiant circuit enveloping a substantial portion of the instrumentality to be heated whereby radiant heat units are transferred thereto, and in then permitting said combustion gases to be released from said closed circuit and brought into direct contact with said instrumentality to be heated thus heating by convection, both the radiant and convected heat being applied to the instrumentality being heated simultaneously and in the same heating zone.

3. A method of heating which comprises maintaining a flow of hot gases of combustion in conduits partially surrounding the instrumentality to be heated whereby radiant within the scope of the invention.

heat units are transferred thereto from three sides of a heating zone, and passing the gases from said conduits into direct contact with said instrumentality to heat it by convection in the same zone.

4. A method of heating which comprises maintaining a flow of hot gases of combustion in heat radiant conduits passing about at least two sides of the instrumentality to be heated, maintaining a countercurrent flow of hot gases of combustion in additional heat radiant conduits also passing about at least two sides of the instrumentality to be heated, whereby said conduits impart radiant heat to said instrumentality and discharging the gases from said conduits into direct contact with the instrumentality to heat it by convect-ion.

LEV A. MEKLER. 

